Ensure correct handling for retraced namespace variables

[guybedford]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevent issue numbers:
Resolves #2413

Description

Fix to ensure that the tracing done through namespaces gets all the same treatment as normal tracing, checking chunking boundaries and included status.

[lukastaegert]

Very nice!

[lukastaegert]

I added a commit to

• Fix the hashes in the chunking-form test
• Make sure the error messages for chunking-form tests include both filename and content
• Set the test that was flaky in Node 6 to require at least Node 8. The error seems to be thrown be acorn when parsing a function overriding a var. Not sure why this sometimes fails and sometimes not.
• Make the watch events test more stable by allowing the event to be triggered more than once in the chokidar case as well. Seems chokidar is not that much better after all.

[guybedford]

Nice, thanks @lukastaegert for those fixes.